Electrical delay switch



May 3, 1960 R. E. SLATER 2,935,588

ELECTRICAL DE'LAY SWITCH Filed Dec. 3, 1957 INVENT OR.

ROBERT E. SLATER BY Way/14 United States Patent O.

h v 2,935,588 ELECTRICAL DELAY swrrcn Robert E. Slater, Sacramento, Calif. Application December 3, 1957, Serial No. 700,392

i Claims. Cl. 200-122 The invention relates to electrical switches and, more particularly, to electrical switches in which the electrical current controlled thereby is causedto stop' flowing after a predetermined interval of time.

Many motorists, to name but one class of persons to whom the device of the invention is found useful, are faced with the following problem upon garaging their cars at night. As the vehicle is driven into a darkened garage, and the car lights are turned off, the motorist is beset by having to walkfrom his ear to the garage light switch in the dark. Even such a short journey, from the automobile to the garage, or house light, is not without its hazards, and is in any event a somewhat unpleasant and groping experience.

ltis therefore an object of the invention to provide a switch in which a motor vehicles headlights are. maintained in illuminated condition for a predetermined length of time after the switch of the invention is actuated' It is another object of the invention to provide a switch in whichan automobiles headlights are turned off at a set time after the switch of the invention is actuated without any further action on the part of the user.

.It is yet another object of the invention to provide a time delay electrical switch applicable not only to motor vehicle headlights but to any compatible electrical system requiring a predetermined period of activation subsequent to removal of manual control.

'It is a further object of the invention to provide a switchwhich is economical to make and install, and yet which is durable and long lived.

It is yet a further object of the invention to provide a time delay electrical switch which is easily integrated into existing electrical systems. i

It is still a further object of the invention to provide a generally improved electrical switch.

Other objects, together with the foregoing, are attairled in the embodiment described in the following description and shown in the accompanying drawings, in which: .1.

Figure 1 is a wiring diagram illustrating how the device itsiincorporatedin a typical automobile headlight installa- Figure-2 normal or open position; and

Figure 3 is a view comparable to Figure 2, but with the switch members in closed and operative position.

While the device of the invention is susceptible of numerous physical embodiments, depending on the environment and requirements of use, substantial numbers of the herein shown and described embodiment have been made and used, and have performed in an eminently satisfactory manner.

Where, as in Figure 1, the switch of the invention, generally designated by the numeral 11, is installed in an automobile headlight system, the device is conveniently mounted on the dashboard (not shown) of the vehicle. Electrical energy is derived from a conventional storage battery 12, the battery having the usual ground potential is a view showing infull line the switch in Ordinarily, a headlight switch 22 is interposed in the line 18.

The delay switch 11 is electrically connected to the system by an input conductor 26 and an outlet conductor 27 wired around the main headlight svn'tch 22 so that.

even though the headlight switch is in off position the headlights can be lit for at least a predetermined period.

Conveniently, the delay switch 11 is shown as including a metallic, or electrical current conducting, housing 31, although it is to be realized that a non-conducting housing could also be utilized provided suitable ground and other leads were incorporated in the switch in a manner readily apparent to one skilled in the art. In the embodiment depicted, however, the housing 31 is appropriately grounded to the vehicle frame, and is therefore a ground or electrically neutral potential.

The inputconductor 26 is suitably connected to an input terminal 33 insulated from the metallic housing 31 as by fiber washers 34, 35, and 36.

Connected to the input terminal 33 and substantially traversing the width of the housing 31 is a conductor 41,

the conductor 41 being secured to a terminal 43 insulated from the housing 31 as by washers 44, 45, and 46.

An electrically energized or activated heat source 51 is interposed in the conductor 41. While any suitable re- .sistance member would serve satisfactorily, a smallincandescent bulb is especially convenient since not only heat but light is thereby produced, the light indicatingan operative status.

Current from the input terminal 33 travels along the Adapted to engage with the switch seat 57 in tight and favorable current-conducting relation is a switch seat 61 mounted adjacentthe endof a somewhat flexible ,tem-

perature responsive member 62, such as 'a bi-metallic strip,

that is to say, two dissimilar metals fastened together,

the coeflicients of expansion of the metals being such that upon being heated to a predetermined temperature the strip 62 tends to swing in a counter-clockwise direction,

as indicated in Figure 3 by the arrow 63. The proximal end of the bi-metallic strip 62 is suitably mounted on a terminal 66 in contact with the housing ,31, and being therefore, at ground potential.

In normal or open, or unheated condition, the'bimetallic strip 62 assumessubstantially the uprightattitude shown in full line Figure 2. When in fully heated condition, however, the strip assumesor is self bent into,ap

proximately the attitude shown in outline in Figure 2.

In order to complete the circuit from the input terminal 33 and through the terminal 43 to the ground potential terminal 66, the switch seats 61 and 57 are urged into tight abutment. A plunger 71 is translatably mounted in a suitable bearing 72 in the housing wall, the plunger 71 terminating at its outer end in a button 73 readily accessible to the user, for example, on the cars dashboard.

The plunger is retained in its normal or open position by a pair of resilient members 75, such as leaf springs mounted on the housing. In norma position, as shown in Figure 2, the springs are spread apart by an annular knob 76, having oppositely sloping end-walls 77 mounted on the plunger 71.

Each of the springs is configured by a hump 78 shaped to correspond to the outline of the knob 76. Thus, when the plunger 71 is urged inwardly to the location indicated in Figure 3, the leaf springs snap inwardly, with the humps 78 confining the knob 76, and thus holding the plunger in its inward position with considerable force, the force being suflicient to overcome the opposing resilient force of the strip 62 so long as the strip is at a temperature below a predetermined temperature.

As is most apparent in Figure 3, inward translation of the plunger 71 into its spring-seated location causes the strip 62 to bend toward the bracket 56 and the seat 61 to move into tight engagement with the seat 57.

At this juncture, current flows from the input terminal 33, through the electrically actuated heat source 51, thence to ground through the terminal 43, the strip 62 and to the ground terminal 66.

The space adjacent the heat source, now activated, shortly becomes heated. Upon the generation of suiticientheat, a temperature responsive or bi-metallic strip 81, of conducting material, secured to the input terminal 33 is caused to bend in the clockwise direction indicated by the arrow 82, in Figure 2. A switch seat 83 on the strip 81 is thereby driven into contact with a corresponding seat 84 on a bracket 86 mounted on an output terminal 87, the terminal 87 being connected to the output wire 27. Appropriate washers 88, 89, and 90 insulate the terminal 87 from the housing 31.

Upon closure of the switches 83 and 84, current flows from the input terminal 33, through the output terminal 87, thence along the output wire 27, and into the headlights 21, causing the headlights to turn on even though the main headlight switch 22 is in off position.

The constants or characteristics of the strip 81 are selected so that but a relatively small amount of temperature rise in the strip 81, produced by the heat source 51, is necessary to efiect closure of the switch seats 83 and 84. Close spacing between the seats 83 and 84 still further tends to cause closure in a short period of time. Consequently, when the operator, upon stopping his car, activates the delay switch by pushing in thebutton 73 and substantially at the same time turns off his light switch 22 (causing his lights to go off) there is a delay but of a few seconds, if any, before the seats 83 and 84 come into contact and the lights again turn on. At this juncture the operator can get out of the car and walk to the garage light switch in the light produced by his head-lamps.

The mechanism described is also effective to turn ofi the head-lamps after a predetermined time interval.

Whereas the strip 81 characteristics and the width of the gap between the seats 83 and 84 are selected so that a very slight temperature rise is sufiicient to close the gap, the characteristics of the strip 62 are chosen so that the temperature of the strip must rise by a considerably greater amount before the strip begins to bend in the direction 63 and thereby breaks the contact between the seats 57 and 61.

Once the strip 62 becomes heated, by the heat source 51, to the necessary temperature, however, the strip commences to bend toward the left and assumes the position shown in outline in Figure 2 (the extent of bending being somewhat exaggerated for purposes of clarity).

As is well recognized, the forces exerted by differential coefiicients of expansion are relatively large. They are, in fact, sufficient to unseat the knob 76 from the confining spring leaf sockets 78, the sloping knob wall 77 camming the springs open to the position shown in Figure 2. Concurrently, the plunger 71 is returned to its off position, shown in Figure 2.

As soon as the contact between the seats 57 and 61 is broken, the heat source 51 is de-energized and the surrounding space cools. As a result of the cooling, the temperature of the strip 81 drops and thus the contacts 83 and 84 are caused to separate, the headlights being thereby turned off.

Upon further cooling, the strip 62 returns to its normal attitude, or central position, shown in Figure 2, awaiting re-activation.

It can therefore be seen that I have provided a small, compact and reliable unit which can readily be installed in any electrical system requiring a delayed action type of operation.

What is claimed is:

1. An electrical switch comprising a substantially closed housing, a first thermally responsive switch in said housing in normally open position, a second thermally,

responsive switch in said housing in normally open position, a heating circuit in said housing including a heat source enclosed by said housing and being adjacent said switches, a manually operable plunger adjacent saidfirstswitch, said plunger being movable between a first position removed from said first switch and a second position against said first switch whereby said first switch closes said heating circuit, a lighting circuit on said housing including said second switch, said second switch being bendable by the elevated temperature. in said housing resulting from activation of said heat source from an open position to a closed position thereby energizing said lighting circuit, said first switch being bendable under the influence of the elevated temperature from a closed position to an open circuit position in said heating circuit.

2. The device of claim 1 wherein said first switch in bending from closed to open position is capable of urging. said plunger from said second position to said first position thereof.

3. The device of claim 2 further characterized by means for holding said manually operableplunger in said second position, said holding means being inetfective to resist the biasing effect of said first switch as said first 1 switch bends from closed to open position under the infiuence of the elevated temperature in said housing.

4. The device of claim 1 wherein said second switch 5 returns from closed circuit position to open circuit position as the temperature within said enclosed housing falls below a predetermined amount.

5. The device of claim 1 wherein said heat source is an incandescent lamp.

References Cited in the file of this patent UNITED STATES PATENTS 

